The present invention relates to a technique for saving electric power in a magnetic disk apparatus. Especially, this invention is suitable for use in a mobile/wearable appliance in which power saving is needed.
With a view to reducing power consumption and speeding up transfer of data in a disk drive apparatus using a flexible disk medium, a technique has been known in which a first-read memory/buffer is prepared, data recorded in the vicinity of data finally demanded is read out of a disk and kept in save in the first-read memory/buffer and rotation drive of the disk is stopped until the data kept in save in the first-read memory/buffer is used or another kind of data is required. This known technique is described in JP-A-9-120617.
A magnetic disk apparatus has been used as a large-capacity memory device in a battery-driven apparatus including a notebook-sized personal computer. In the battery-driven apparatus and the magnetic disk apparatus built therein, power saving is needed for the purpose of increasing usable time assured by one charging operation. In a conventionally known method in which rotation of the disk is stopped during stoppage of recording/reproduction, there arises a problem that when a request for recording/reproduction is made with the disk placed in stop condition, much time is required and high power is consumed to start operation. Further, in the magnetic disk apparatus, the head has to be set back to a retreat position and time is also consumed for this purpose. Accordingly, frequent retreat of the head cannot be allowed.